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Questions and Answers
What is the purpose of adding NaF (sodium fluoride) to water?
Which of the following tests is used to identify the presence of carbonate anions?
What is the result of adding BaCl₂ to a solution containing sulfate anions?
What is the purpose of adding a few drops of dilute ammonia solution to a solution containing chloride anions and AgNO₃?
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What is the result of mixing a nitrate solution with cold concentrated H₂SO₄?
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What is the result of adding dilute Hydrochloric acid to a carbonate or a Hydrocarbonate compound?
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What is the purpose of adding ammonium molybdate in the test for Phosphate (PO₄³⁻) anion?
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What is the characteristic of covalent compounds that allows them to conduct electricity when molten or in solution?
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What is the term for the ability of an atom in a covalent bond to attract the shared pair of electrons?
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What is the type of bond that is formed when the difference in electronegativity values between atoms is greater than 1.7?
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Why is it essential to use the minimum amount of hot water when dissolving benzoic acid crystals?
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What happens when the benzoic acid solution is cooled to room temperature and then placed in iced water?
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What is the purpose of filtering the solution by vacuum filtration?
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What is the effect of impurities on the melting point of benzoic acid?
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What is the expected melting point range of pure benzoic acid?
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Study Notes
Importance of Salt
- Isotonic salt tablets are taken by athletes to replace salt lost through sweating
- Brine (salt solution) is used to preserve foods such as bacon
- NaF (sodium fluoride) is added to water to prevent tooth decay
Identification of Anions
Tests for Various Anions
- Carbonate and Hydrogencarbonate: Add dilute HCl to the solution, and a gas is produced that turns limewater milky
- Carbonate: Add BaCl₂ to the solution, and a white precipitate forms
- Hydrogencarbonate: Add BaCl₂ to the solution, and a white precipitate forms on heating
- Sulfate: Add BaCl₂ to the solution, and a white precipitate forms that is insoluble in dilute HCl solution
- Sulfite: Add BaCl₂ to the solution, and a white precipitate forms that is soluble in dilute HCl solution
- Chloride: Add AgNO₃ to the solution, and a white precipitate forms that is soluble in dilute NH₃ solution
- Nitrate: Mix the solution with cold concentrated H₂SO₄, and a brown ring forms
- Phosphate: Add ammonium molybdate reagent and concentrated nitric acid, heat gently, and a yellow precipitate forms that is soluble in ammonia solution
Properties of Covalent Compounds
- Most are liquids or gases at room temperature, or solids with low melting and boiling points
- They do not conduct electricity when molten or in solution because they do not break up to form ions
- Most covalent substances do not dissolve readily in water
Electronegativity
- Electronegativity is the relative attraction of an atom for the shared pair of electrons in a covalent bond
- Electronegativity values can be used to determine which atom will have the greater attraction on the shared pair of electrons
- Examples: Hydrochloric acid (H-Cl) has a polar covalent bond, with chlorine having a greater electronegativity value
Predicting Bonds
- Electronegativity values can be used to predict the type of bond that will be formed between atoms
- The greater the difference in electronegativity values between atoms in a bond, the greater the degree of polarity
- Examples:
- Non-polar covalent bond: CS₂, Cl₂
- Polar covalent bond: HBr
- Ionic bond: NaCl
Recrystallization of Benzoic Acid
- Benzoic acid is a crystalline solid that is very soluble in hot water but only slightly soluble in cold water
- The experiment involves dissolving the original crystals, removing impurities, and recrystallizing pure benzoic acid crystals
- The final mass of the crystals is measured, and the melting point of the recrystallized benzoic acid is found
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Description
Test your knowledge of inorganic compounds with these questions about sodium fluoride, carbonate anions, and sulfate anions.
